In any well for the production of hydrocarbon products from a subterranean reservoir, over a period of time the production rate will tend to decrease. This decrease is attributable to many factors. However, at least some of them can be overcome so that a desired production rate can be restored or maintained.
Often the decrease in production is attributable to conditions within the hydrocarbon holding substrate. This condition can frequently be narrowed to the lack of reservoir pressure sufficient to urge the product through substrate, to the well, and to the surface.
There are other factors which are known to contribute to the decrease in production, most of which can be countered or overcome through appropriate well treatment. One such treatment includes the injection pressure of a stimulating fluid into the well, which fluid is in turn forced into the substrate. The result will normally be a thinning of the product's viscosity in the instance of crude oil. Thus, reservoir pressure will be capable of pushing the less dense product to the surface.
An example of a typical well stimulation procedure embodies the injection of chemicals into the well in sufficient amounts and proportions, and over a set period of time to effect the desired stimulation function. While chemical injection is an accepted way of dealing with a production problem, the presence of chemicals downwell often creates an undesirable, deleterious or corrosive atmosphere. The latter will eventually be unacceptable for equipment that must function in this atmosphere.
In the instance of equipment which embodies fluid tight connections, where the seal is fabricated of a nonchemically resistant material, it will deteriorate to the point where it is no longer capable of functioning.
In one such instance, when carbon dioxide is injected into or produced from a well, the generation of a corrosive atmosphere downhole, will preclude the use of most deformable or pliable seal materials in connections. Functionally, the latter are normally squeezed into a compressed state at a separable joint to effectuate a barrier to passage of the injected or product fluid.
In other instances when such a seal is employed at a fluid tight joint, the chemical affect of CO.sub.2 in the seal itself, will cause the seal to deteriorate or to expend. When this occurs, the seal material could bond with the adjacent metallic parts, thereby prohibiting subsequent separation of the parts when the seal is to be broken. The cost of cleaning the well to overcome such a condition, and the damage to the equipment involved can be a costly experience.
Toward overcoming this problem in the periodic treatment of a well for stimulating production or enhancing product recovery, the present seal is adapted for use in a downhole situation exhibiting a corrosive atmosphere. The seal is formed in an elongated pipe string and includes a lower pipe segment which is prepositioned within a well. The lower segment includes an upwardly facing receptacle or socket.
An upper segment of the pipe string which conducts the pressurized flow of treating or produced fluid, includes a connector comprised of one or more rings or gaskets of a deformable, preferably extrudable soft metal. The metallic seal ring or rings are positioned on the connector to sealably engage corresponding surfaces in the upfacing receptacle.
As the heavy upper pipe segment descends into the well, it will bear against and cause the deformable metal ring or rings to be extruded into an annular extrusion space or chamber. The latter is defined between corresponding surfaces of the receptacle and the connector respectively.
Subsequent to the softer metal extrusion phase, further lowering of the pipe string upper segment will end when the connector face contacts a corresponding hard metal surface of the receptacle to form a circular, metal-to-metal line seal.
It is therefore an object of the invention to provide a metal-to-metal downhole seal for a packer and/or a pipe string or the like which is adapted to function in a deleteriously corrosive atmosphere.
A further object is to provide a downhole well seal for a packer or pipe string having at least one separable joint which is formed by a hard metal seal, together with and in cooperation with a soft metal extruded gasket seal.
A still further object is to provide coacting hard and soft metal seals in a downhole packer and/or pipe joint, wherein the softer metal is extruded until the hard metal seal is established, thereby to preclude further movement of the pipe segments toward each other.